Noxious Weed IVM Guide Contents, IVM for Noxious Weeds
Broom, Canada Thistle, Gorse, Knapweeds, Leafy Spurge, Purple Loosestrife,
Purple Starthistle, Smooth Cordgrass, Tansy Ragwort, Yellow Starthistle
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IVM Technical Bulletin

Chemical Controls
In IVM programs, herbicides are considered transition tools that enable the manager to suppress weeds and replace them with desirable, competitive vegetation. Thus, it is important to select the least-toxic, low-residual herbicide that is effective against the target weed, and to apply them in a judicious manner.

Use Herbicides Properly
Use herbicides in accordance with their EPA-approved label directions. Protective gear should always be worn when applying herbicides, and applicators should be certified to apply pesticides. Maintain labels and Material Safety Data Sheets (MSDS) of the pesticide products on file. For the purpose of this bulletin, specific chemicals will not be discussed. Chemical name brands and registrations change constantly and the concentrations of chemicals allowed by each state varies. We believe the choice of chemicals and concentration levels is site-specific and differs too widely to be encompassed by any one bulletin. Check the label to make sure that the product you choose is registered for the site you are treating. Consult the Cooperative Extension Service, State Agricultural Experiment Stations, or County Agriculture Commissioner for specific herbicide recommendations and information on their use in particular localities.

Herbicide Information Resources
Information on herbicides can be found in the Herbicide Handbook, Federally Registered Pesticides, Farm Chemicals Handbook, Montana-Utah-Wyoming Weed Management Handbook, The Pacific Northwest Weed Control Handbook, and The Pesticide Manual (see Pesticide Information Resources). These publications list specific information on the chemical and physical properties of active ingredients as well as recommendations and precautions for use.

Criteria for Selecting an Herbicide
When choosing an herbicide, it is essential to avoid or minimize negative impacts on non-target organisms, including the capability of the soil to support desirable vegetation. Remember, the site (croplands, rangelands, rights-of-way, etc.) you plan to treat must be listed on the label. The following questions are useful when making a site-specific decision about which herbicide to use.

Is the herbicide:

  • effective against the target species?
  • least-toxic to humans and other non-target organisms such as desirable vegetation, animals, and beneficial insects?
  • one that requires a surfactant? If so, is the surfactant safe to use in areas with sensitive organisms such as salamanders and other amphibians?
  • least-likely to leach into ground or surface water?
  • compatible with vegetation and revegetation programs?
  • compatible with other management methods?
  • low in volatility so drift is minimized?
  • quickly degraded in the soil?
  • cost effective?

  • Application Methods
    In IVM programs, spot-treatment rather than broadcast application over wide areas is the preferred herbicide application method. Spot-treatment consists of various techniques for applying herbicides to target weeds without impacting desirable vegetation or other non-target organisms. Spot-treatment can reduce herbicide use, lower costs, lower risks to non-target organisms including humans, and reduce drift. Broadcast herbicide applications are recommended only when necessary (e.g., where weed infestations are very dense and extensive, or when plant fuel must be dry prior to controlled burns). In a weed containment program, herbicides can be useful as a "border" spray to prevent infestations from moving into non-infested areas.

    Last modified:  August 17, 2000
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